Janne Ouwehand studies a powerful bird lighter than three sugar cubes. The tiny pied flycatcher migrates from West Africa to Europe to breed in spring, flying more than 5,000 kilometers in about two weeks. Their mission? To reach Europe in time for the caterpillar peak, as the insects are the main food source for their chicks.

The springtime caterpillar peak in western Europe is “a very short time window of about one to three weeks,” Ouwehand says at TEDxUniversityofGroningen. Pied flycatcher offspring depend on caterpillars, she says, so migration timing is crucial for these tiny birds.

Hungry pied flycatcher chicks (Photo: Axel Strauß)

But with climate change affecting spring temperatures and caterpillar hatching times, the birds have been hit hard, Ouwehand says. A study in 2006 found that in areas where caterpillar peaks shifted earlier, there was a pied flycatcher population decline of 90 percent over two decades. Four years later, flycatcher researcher Christiaan Both found the birds had begun to adjust their breeding times to fit warming temperatures and caterpillar peaks: “Breeding dates have become progressively earlier,” he says, “and birds are thus born earlier in the spring.”

But Ouwehand and others are worried about how fast the birds can adapt to rapid climate change. She is searching out how birds could dramatically alter their migration patterns — “the complex decisions that go into migration,” she says.

Developing a study of these patterns has been challenging, she says, because “when you’re in Africa, you can’t tell [by looking at a bird], which bird comes from where.” As a stop-gap solution, she fit birds in breeding grounds in the Netherlands with “mini backpacks” — small sensors for the birds to wear on their trip to Africa.

Pied flycatcher tracker backpack (Photo: Janne Ouwehand)

The “backpacks” are half a gram and detect temperature and light. When a backpack is recovered from a returning bird, Ouwehand can use the sensor data to estimate a bird’s travel pattern. Ouwehand learned that the birds fly over the Sahara in marathon 40-60 flights at very high altitudes and speeds to avoid “the extreme climate of the desert.” This trip probably couldn’t be sped up any further, she says, but the jury is still out on whether they can leave earlier. “We do not very well understand whether they [can],” she says.

Janne Ouwehand with a backpack-wearing bird (Photo: Janne Ouwehand)

“Probably, we can’t give one single answer on whether this bird can really adapt to climate change,” Ouwehand says. But by studying the lives of birds and other animals affected by climate change, we can get to know “the constraints of these living organisms to respond to such enormous changes like global warming.”

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